OBJECTIVESPrevious types of rock wool has been recently replaced with high-temperature wool (HT wool). HT wool is characterized by a chemical composition with a higher concentration of Al(2)O(3) and a lower concentration of SiO(2), lower biopersistence, and a higher melting point than previous types of rock wool. To evaluate the safety of HT wool, an asbestos substitute, we examined the biopersistence of HT wool in the lungs, based on changes in fiber count according to the length and fiber size (length and width), by performing a nose-only inhalation exposure study in rats.

METHODSMale Fischer 344 rats were exposed to fibers at the target exposure concentration of 30 mg/m(3) continuously for 3 hours daily for 5 consecutive days. Rats were sacrificed shortly after exposure, and 1, 2, and 4 weeks after exposure, and their lung tissues were incinerated at a low temperature. Then, fiber counts and sizes in the lungs were analyzed using a phase contrast microscope.

RESULTSThe fiber count in the lungs 4 weeks after exposure significantly decreased from the baseline value (shortly after exposure). The half-life of fibers calculated from the approximation curve was 34 days for all fibers and 11 days for fibers longer than 20 μm.

CONCLUSIONSBoth the length and width significantly decreased 4 weeks after exposure, probably because fibers were ingested by alveolar macrophages, discharged to outside of the body by mucociliary movement, or lysed by body fluid. In future studies, it is necessary to examine the long-term persistence of fibers in the lungs.

OBJECTIVETeeth can serve as records of environmental exposure to heavy metals during their formation. We applied a new technology - synchrotron radiation microbeams (SRXRF) - for analysis of heavy metals in human permanent teeth in modern and historical samples.

METHODSEach tooth was cut in half. A longitudinal section 200 mum in thickness was subjected to the determination of the heavy metal content by SRXRF or conventional analytical methods (ICP-MS analysis or reduction-aeration atomic absorption spectrometry). The relative concentrations of Pb, Hg, Cu and Zn measured by SRXRF were translated in concentrations (in g of heavy metal/g of enamel) using calibration curves by the two analytical methods.

RESULTSConcentrations in teeth in the modern females (n = 5) were 1.2 +/- 0.5 mug/g (n = 5) for Pb; 1.7 +/- 0.2 ng/g for Hg; 0.9 +/- 1.1 mug/g for Cu; 150 +/- 24.6 mug/g for Zn. The levels of Pb were highest in the teeth samples obtained from the humans of the Edo era (1603-1868 AD: ) (0.5-4.0 mug/g, n = 4). No trend was observed in this study in the Hg content in teeth during 3,000 years. The concentrations of Cu were highest in teeth of two medieval craftsmen (57.0 and 220 mug/g). The levels of Zn were higher in modern subjects (P < 0.05) than those in the Jomon (~1000 BC: ) to Edo periods [113.2 +/- 27.4 (mug/g, n = 11)]. Reconstruction of developmental exposure history to lead in a famous court painter of the Edo period (18th century) revealed high levels of Pb (7.1-22.0 mug/g) in his childhood.

CONCLUSIONSSRXRF is useful a method for reconstructing human exposures in very long trends.

OBJECTIVESThe objective of this study was to evaluate factors associated with turnover intention among nurses in small and medium-sized medical institutions.

METHODSA self-administered questionaire survey was performed in 293 registered nurses, licensed practical nurses, and assistant nurses working full-time in various medical institutions. Multiple linear regression analysis was conducted, with turnover intention as the dependent variable, and nurses' basic attributes and job satisfaction as independent variables.

RESULTSAs for nurses' basic attributes, turnover intention was significantly associated with registered nurses, younger nurses and those with low satisfaction with sleep. As for nurses' job satisfaction, the number of nurses with turnover intention was significantly higher for those with low satisfaction with salary, low satisfaction with welfare, poor implementation of fair salary raise and poor cooperation among nurses.

CONCLUSIONTurnover intention may be reduced by the enhancement of trust in the organization, giving appropriate advice to young nurses and registered nurses, and developing measures for addressing sleep disorders.